Fire protection apparatus

ABSTRACT

A COMPLETELY AUTOMATIC FIRE PROTECTION SYSTEM IS DISCLOSED COMPRISING BATTERY POWERED, PORTABLE SUPPRESSOR UNITS EACH INCLUDING A SUPPLY OF FIRE EXTINGUISHING FLUID AND A FIRE DETECTOR. CONNECTION OF THE INDICIDUAL UNIT&#39;&#39;S CONTROL CITCUITS PROVIDES A CONTROL CIRCUIT NETWORK THAT AUTOMATICALLY INITIATES EXTINGUISHING FLUID DISCHARGE FROM ALL UNITS IN RESPONSE TO FIRE DETECTION BY ANY SINGLE UNIT.

Sept. 20, 1971 J, GRABQWSKI ETAL 3,605,901

FIRE PROTECTION APPARATUS Filed oct- 28. 1958 I 4 ShOQtS-Shbflt 2 wxilauuflflaboaflw, Rea fovol 14116081 Sept. 20, 1911 Filed Oct. 28. 19

G. J. GRABOWSKI E AL FIRE PROTECTION APPARATUS 4 Sheets-Sheet 5 6003190 J: 6340210196, Wiliaiam B. 062103 320,

ford wl'afi'ow,

I I l I l I I I I I I I I l I I I l I I I I l I l I I I I I 4 Sheets-Shoat 4 6. J. GRABOWSKI ETAL FIRE PROTECTION APPARATUS Iwezatovm fleoflgelfirabomi'di, wiwnflflsfiovne, Berg-02 d Wileow,

fltior zzey Sept. 20, 1971 Filed Oct. 28. 1968 United States Patent Office 3,605,901 Patented Sept. 20, 1971 3,605,901 FIRE PROTECTION APPARATUS George J. Grahowslri, Needham, William B. Osborne, Marlboro, and Rexford Wilson, Framingham Centre, Mass., assignors to Fenwal, Inc., Ashland, Mass.

Filed Oct. 28, 1968, Ser. No. 770,926 Int. Cl. A62c 35/00 US. Cl. 1692R 11 Claims ABSTRACT OF THE DISCLOSURE A completely automatic fire protection system is disclosed comprising battery powered, portable suppressor units each including a supply of fire extinguishing fluid and a fire detector. Connection of the individual units control circuits provides a control circuit network that automatically initiates extinguishing fluid discharge from all units in response to fire detection by any single unit.

BACKGROUND OF THE INVENTION This invention relates generally to fire protection apparatus and, more particularly, relates to a portable, fully automatic fire extinguishing device that can be used either independently or in groups to provide a complete fire protection system.

There exist various circumstances wherein temporary fire protection is desired for particularly valuable objects. Examples of such objects include grounded and unoccupied aircraft, partially constructed buildings, temporarily stored high value equipment such as electronic gear, etc. In addition to these applications, a completely portable, automatic fire protection system could be used to protect valuable cargo being transported, for example, on aircraft, trailers, railroad cars, ships, etc. or in some instances to protect an existing installation in circumstances wherein the incorporation of a permanent fire extinguishing system would prove economically unwarranted.

Previous portable fire protectionv devices have included either automatic detectors that produce an alarm in response to fire conditions or manually operated fire extinguishers. No portable system exists, however, which is capable of both automatically detecting and quickly extinguishing an existing fire. Because of this deficiency flame, heat and smoke damage in the above noted applications is relatively common. Furthermore, the relatively slow response associated with present fire protection methods results frequently in both water and fire fighting damage to the protected equipment or structures.

The object of this invention, therefore, is to provide a fully automatic, self-contained and portable fire extinguishing apparatus which can be easily transported to and installed in an area wherein temporary fire protection is desired.

CHARACTERIZATION OF THE INVENTION The invenion is characterized by the provision of a portable fire suppressor including a fire extinguishing medium filled container, a valve for controlling discharge of the fire extinguishing medium, a condition responsive detector, and an actuator adapted to open the valve and produce discharge of the fire extinguishing medium in response to activation by the condition responsive detector. By merely transporting the portable suppressor to a selected location, the immediately enclosing volume is provided with fully automatic and quickly responsive fire protection.

One feature of the invention is the provision of a portable fire suppressor of the above type including an extendible hollow mast connected for fluid communication between the extinguishing medium filled container and a discharge orifice. Upon contraction of the mast, the suppressor is extremely compact and can be easily stored or moved to an area of intended use after which extension of the mast provides a fluid extinguishing medium discharge orifice at a particularly desired height.

Another feature of this invention is the provision of a portable suppressor of the above featured type wherein the condition responsive detector is a fire detector mounted on the discharge orifice end of the extendible mast. According to this arrangement, the detector is automatically positioned at a suitable position near the top of the protected zone.

Another feature of this invention is the provision of a portable fire suppressor of the above featured types including a discharge head having a plurality of openings that form the discharge orifice and establish a uniform discharge of the extinguishing medium. According to an additional feature, the discharge head openings form the primary restriction to fluid flow in the discharge path including the valve and extendible mast. Thus, upon use of a liquified gas extinguishing medium, heat absorbing evaporation occurs externally and problems of internal freeze-up are obviated.

Another feature of this invention is the provision of a portable fire suppressor of the above featured types including an electrical control circuit responsive to the fire detector and operable to activate the fluid medium discharge actuator. Also included in the control circuit is a self-contained source of electrical power. Incorporation of a battery powered control circuit permits efiicient automatic operation of the suppressor in even remote locations where electrical power is not available.

Another feature of this invention is the provision of a fire protection system formed by a plurality of portable fire suppressors of the above featured types. According to this embodiment of the invention, electrical leads are utilized to connect corresponding control circuit terminals of a plurality of suppressor units and the resultant control circuit network is adapted to produce sympathetic actuation and resultant extinguishing medium discharge from all units in response to fire detection by any of the associated fire detectors. By strategically locating the individual suppressor units, a completely automatic fire extinguishing system can be established for a protection zone of any size and configuration.

Another feature of this invention is the pro-vision of a fire protection system of the above featured type and including an alarm station and an end-of-line station connected to opposite ends of the suppressor array. The combined circuitry of the alarm station, the end-of-line station and the suppressor unit are adapted to produce a signal at the ramp alarm station in response to a variety of trouble conditions existing anywhere in the zone protected by the complete system.

Another feature of the invention is the provision of a fire protection system of the above featured type wherein the ramp alarm system is adapted for connection to a source of alternating current power that under normal conditions provides charging current to the batteries in all of the detector units. With this system, fully charged batteries are insured at all times. In addition, the control circuit of each suppressor includes a capacitor that stores energy received from the AC. source and is effective to activate the valve actuator in the absence of battery power.

Another feature of the invention is the provision of a fire protection system of the above featured types wherein the suppressor control circuits are adapted to isolate the individual batteries from each other thereby preventing the drain of power from one unit to another in which a faulty battery circuit exists.

DESCRIPTION OF THE DRAWINGS These and other objects and features of the present invention will become more apparent upon a perusal of the following specification taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic block diagram illustrating a preferred embodiment of the invention;

FIG. 2 is a schematic view of one of the suppressor units shown in block form in FIG. 1;

FIG. 3 is a schematic circuit diagram of the ramp alarm station shown in FIG. 1;

FIG. 4 is a schematic circuit diagram of a suppressor unit control circuit shown in FIG. 1;

FIG. 5 is a schematic circuit diagram of the detector circuit shown in FIG. 2; and

FIG. 6 is a schematic circuit diagram of the end-ofline station shown in FIG. 1.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1 there is shown a block diagram of a preferred embodiment of the invention. The fire protection system 11 includes the plurality of suppressor units 12 connected by the electrical cables 13. As more fully described below, each of the suppressors 12 is a self-contained, automatic unit including a source of extinguishing medium and a fire detection control system capable of inducing discharge of the extinguishing medium in response to detection of a fire. In addition, the individual units 12 are completely portable and can be selectively distributed in any manner desired. Thus, the number and arrangement of the indiyidual units 12 can be selected such that the entire system 11 provides fire protection for a zone of any configuration or size. Terminating opposite ends of the system 11 and also connected by electrical cables 13 are the ramp alarm station 14 and the end-of-line station 15 which also are described in detail below.

FIG. 2 schematically illustrates one of the suppressor units 12, all of which are identical. As shown, the unit 12 includes a portable base housing 18- with carrying handles 19. Retained within the housing 18 is the container tank 21 filled with a suitable fire extinguishing medium 20. Although other agents such as water or dry chemicals can be used, preferred extinguishing mediums are halogenated, liquified gases such as Freon FE 1301 (CBrF which is marketed by the DuPont Co.

Extending into the tank 21 and having a discharge port 22 disposed adjacent the bottom thereof is the hollow discharge tube 23. The hollow extendible mast assembly 24 is connected to the discharge tube 23 by the valve unit 25. Preferably, the valve unit 25 is activated by an electrically energized explosive squib. Valves of this type are conventional and shown, for example, in US. Pat. No. 2,712,881. As shown, the mast assembly 24 includes a plurality of hollow mast sections 26 joined by fluid tight couplings 27. The upper mast section 28 supports the discharge head 29 having a plurality of openings 31 that define a discharge orifice. Supported by the discharge head 29 is the fire detector 32 described more fully below.

Also mounted within the housing 18 on the support bracket 33 is the circuit housing 34 having a control and indicator panel 35. Extending into the housing 18 and connected to the circuitry in the circuit box 34 is the electrical cable 13 that terminates with the multi-pronged plug 36. Also connected with the circuitry in the circuit box 34 are the battery 37 and the plug receptacle 38 that is adapted to receive an electrical plug identical to plug 36. Also connected to the circuitry in circuit box 34 are both the detector unit 32 by the elongated cord 40 that permits extension of the mast assembly 24 and the explosive squib 39 of the valve unit 25. All the circuitry retained by the housing 18 is shown in the schematic circuit diagram of FIG. 4 and is described in detail below.

The suppressor unit 12 can be used either as an individual self-contained, automatic fire extinguishing device or can be combined with other units in a system as shown in FIG. 1. When used individually, the suppressor 12 is manually transported by the carrying handles 19 to an area where fire protection is desired. During storage or movement of the suppressor unit 12, the mast assembly 24 is maintained in a compact condition with the individual mast sections 26 dismantled. However, after placement for intended use, the mast assembly 26 is extended by connecting together the desired number of mast sections 26. Final positioning of the discharge head 29 and detector unit 32 near the ceiling of the protected zone is accom plished by adjustment of mast section 28 which is slideably received by the adjacent mast section 26. The detector 32 may be, for example, 5 to 10 feet above the surface supporting the housing 18. Obviously, the desired extendibility also can be obtained with a mast assembly composed entirely of telescopic sections.

This is an important feature of the invention in that actuation of a valve unit 25 will induce discharge of the fire extinguishing medium 20 through the discharge head 29 that is positioned above the protected area. Since most desirable extinguishing agents are heavier than air, discharge above the protected zone is the most efficient meth- 0d of extinguishment. Furthermore, the detection eflicency is improved by placement of the detector 32 above the protected zone since the products of combustion such as smoke and heat are lighter than air and will accordingly be most easily detected near the top of the protected zone.

After detection of fire by the detector unit 32, the control circuit in the circuit box 34 responds, as described below, to energize the explosive squib 39 and open the valve 25. This permits the vapor pressure within the tank 21 to force extinguishing liquid up through the discharge port 22, the discharge tube 23, the hollow mast assembly 24 and out of the openings 31 in the discharge head 29. Thus, the protected zone is permeated with the agent 20 and the detected fire is extinguished. As another feature of the invention, the discharge openings 31 comprise the greatest restriction to fluid flow in the discharge path including the mast assembly 24, the valve 25 and the discharge tube 23. Consequently, heat absorbing vaporization of the extinguishing agent 20 occurs externally and the possibility of fluid flow restricting freeze-up in internal portions of the device is obviated.

When the suppressor 12 is used in a system application as illustrated in FIG. 1, the individual units 12 are merely connected in series by inserting the plug 36 of one unit into the receptacle 38 of another and end units are similarly connected respectively, to a ramp alarm station 14 and an end-of-line station 15. The attached units 12 are selectively distributed so as to provide coverage of the entire area to be protected. Because of the flexibility provided by the connecting cords 13', a number and arrangement of units 12 can be selected to protect a zone of any size and shape.

Upon detection of a fire by any of the detectors 32, the connected control systems are effective, as described below, to actuate the valves 25 of all suppressors 12 and flood the entire area with extinguishing agent 20. The separation between units 12 is selected such that the volumes filled with extinguishing agent 20 by the individual suppressor units 12 will overlap and thereby provide complete coverage of the protected zone. When using the above noted liquified extinguishing gases, it is preferred that after complete discharge of all units 12 the protected zone will contain a substantially uniform concentration of the extinguishing vapor in an amount of between 2 and 5% by volume.

Referring now to FIG. 3 there is shown a schematic circuit diagram of the ramp alarm station 14 shown in FIG. 1. The primary of transformer 43 is connected between grounded line 44 and line 45 which in turn are connected to a suitable source of AC. power. Also connected in series across A.C. input lines 44 and 45 are the signal light 46 and the normally closed switch contacts 47. The A.C. input lines 44 and 45 are connected also, respectively, to output terminals C and D. Connected between output terminals B and E is the series combination of the secondary winding of the transformer 43 and the relay winding 48 associated with contacts 47. Between A.C. input line 44 and output terminal H are connected in series the battery 49, the relay winding 51 and the diode 52. Normally open switch contacts 53 operated by the relay winding 51 are connected in series with the diode 54 and the alarm horn 55 across the battery 49. The manually operated switch contacts 56 are coupled directly across output terminals H and E.

FIG. 4 schematically illustrates the control circuitry 30 included within the suppressor housing 18 shown in FIG. 2. Input terminals B, H, E, C and D are connected directly to the corresponding output terminals in the ramp alarm station 14 (FIG. 3) by signal lines in the electrical cord 13. Coupled directly to the input terminals H, E, C and D of the suppressor control system 30 by lines 6063 are its corresponding output terminals H, E, C, and D while input termnial B an doutput terminal B are linked, respectively, to the detector terminals 64 and 65. The A.C. supply lines 62 and 63 are connected to the primary winding of the transformer 66 having a secondary winding coupled across the input terminals of the diode rectifier bridge 67. Connected across the output terminals of the rectifier bridge 67 through the limiting resistor 68 is the parallel combination of the capacitor 69 and the battery 37 (shown in FIG. 2).

Also coupled across the output terminals of the battery 37 is the series combination of the relay winding 71 and associated normally open switch cont-acts 72 and the diode 73. The junction between the diode 73 and the relay winding 71 is connected by line 74 to the detector terminal 75 while the junction between the diode 73 and the switch contacts 72 is connected to input terminal E. Connected in parallel between input terminal E and the negative output terminal 76 of the battery 37 are the series connected diode 77 and alarm horn 78 and the series connected diode 79 and valve operating explosive squib 39 (shown in FIG. 2). The other detector terminals 81 and 82 are connected, respectively, to input terminal H and the negative output terminal 76 of the battery 37. The manually operated switch contacts 83 are connected between input terminal E and input terminal H which is also connected by line 60 to the positive output terminal 84 of the battery 37.

FIG. shows schematically the circuitry included in the detector unit 32 shown in FIG. 2. The input terminals 64, 65, 75, 81 and 82 are directly connected to the corresponding detector terminals in the suppressor control system 30 (FIG. 4) by electrical lines in the electrical cable 40. Connected in series between the terminals 64 and 65 are the normally open switch contacts 91 and the normally closed switch contacts 92. The relay winding 93 associated with normally open switch contacts 91 a the series combination of the relay winding 94 associated with normally closed switch contacts 92 and the combustion products detector 95 are connected in parallel across terminals 81 and 82. Directly connected between terminals 75 and 81 is the fire detector 97. Both the combustion products detector 95 and fire detector 97 are conventional and can comprise any of the well known types of fire detectors. In a preferred embodiment, detector 95 is a smoke responsive ionization switch and detector 97 is a rate compensated thermally actuated switch.

FIG. 6 shows a schematic diagram of the circuitry included in end-of-line unit shown in FIG. 1. The terminals B, H, E, C and D are connected directly to the corresponding output terminals of the suppressor control system shown in FIG. 4. Connected across terminals C and D is the primary winding 101 of the transformer 102. The secondary winding 103 is connected in series with the relay winding 104 between one end of the primary winding 101 and the terminal H. Connecting terminals B and E are the normally open switch contacts 105 associated with the relay winding 104.

In the interest of simplicity, the suppressor control system 30 shown in FIG. 4 is described as connected directly between the ramp alarm station 14 shown in FIG. 3 and the end-of-line station 15 shown in FIG. 5. It will be appreciated, however, that any desired number of suppressor units 12 which are identical in construction and performance, can be connected in series between the ramp alarm station 14 and the end-of-line station 15. The dc sired number are joined by merely inserting the plug 36 (FIG. 2) of one unit into the receptacle 38 of the next unit thereby automatically connecting corresponding terminals of the adjacent units. For example, after connection of two identical units having control circuits 30 as shown in FIG. 4, the input terminals B, H, E, C and D of one unit are connected, respectively, to the output terminals B, H, E, C and D of the directly adjacent unit.

After strategic deployment of the individual suppressor units 12, the A.C. input lines 44 and 45 in the ramp alarm station 14 are energized to activate the A.C. portion of the system. This creates an A.C. potential across lines 62 and 63 (FIG. 4) in each suppressor unit 12 of the system. Consequently, the transformer 66 applies a voltage to the bridge 67 which produces a DC. output current between output terminals 76 and 84. This current trickle charges the battery 37 insuring its effectiveness over long periods of use. The output of the bridge circuit 67 also charges the capacitor 69 with sufficient electrical energy to operate the system, as described below, in the event that battery 37 is inoperative.

In the absence of fire, the valve actuating squib 39 is isolated from battery voltage by the normally open switch contacts 72 and 83. However, upon the occurrence of fire in the immediate vicinity of a suppressor unit 12, the resultant heat closes the heat responsive contacts 97 in the associated detector unit 32 (FIG. 5). This creates across the battery 37 a complete circuit including line 60, terminal 81, closed contacts 97, terminal 75, and relay winding 71. The resultant energization of the relay winding 71 locks in the latching type contacts 72 completing a circuit through both the valve actuating squib 39 and the alarm horn 78. Consequently, an alarm is sounded and the squib 39 actuated to open the valve 25 (FIG. 2). This in turn permits discharge of the extinguishing agent 20 through the openings 31 in discharge head 29 as described above.

In addition, since terminals H and H of each suppressor 12 within the system 11 are connected directly in series as are terminals E and E. closing of switch contacts 72 in one unit automatically completes a circuit between terminals H and E in all suppressors 12. Consequently, the alarm horn 78 and valve actuating squib 39 of each unit are energized so that all suppressors sound alarms and discharge their extinguishing agents 20. Accordingly, the entire zone protected by the selective deployment of the various suppressor units 12 is flooded with extinguishing medium in response to detection of fire by any one unit of the system.

Since closing of the latching contacts 72 anywhere in the system also connects terminals H and E in the ramp alarm station 14 (FIG. 3), the alarm horn 55 is energized to provide an audible alarm signal. This occurs because of the circuit completed through the battery 49, the diode 52, and the relay winding 51 which is thereby energized to close the normally open contacts 53 and permit current flow to the alarm horn 55. This same sequence of operation is accomplished manually at any suppressor unit 12 by closing its switch contacts 83 to complete a circuit between terminals H and E. Similarly, the system can be activated at the ramp alarm station 14 (FIG. 3) by closing manually operated switch contacts 56. It will be noted 7 that the diodes 73, 77 and 79 in each suppressor control circuit 30 isolate and prevent current flow between batteries located in other circuits. Thus, one faulty battery will not drain power from and deactivate the batteries of other suppressors 12 of a protection system 11.

Because operating power is supplied by the batteries 37, operation is insured even in the absence of an AC. power source. Therefore, a system capable of functioning in the manner described above can be formed by connecting together an array of suppressor units 12 without either the ramp alarm station 14 or the end-of-line station 15. Further functions provided by these components are described below. It will be obvious also that a single suppressor 12 will function as described in the absence of any additional connected units.

Referring again to FIG. 3, the energization of the signal light 46 in response to closing of contacts 47 is an indication that any one of a number of fault conditions exists. The normally closed switch contacts 47 are opened to deactivate the trouble light 46 in response to energization of the relay winding 48. This winding 48 is normally energized by secondary current from the transformer 43 flowing in a trouble circuit that includes lines connecting the B terminals of all suppressor units in the system 11, lines joining detector terminals 64 and 65 and including switch contacts 91 and 92 in each suppressor 12 (FIG. switch contacts 105 in the endof-line station 15 (FIG. 6) and lines joining the E terminals of all units. However, the existence of smoke in the vicinity of one suppressor unit 12 activates the smoke detector 95- (FIG. 5) of its associated detector 32. This closes the smoke detector contacts and completes a circuit through relay winding 94 across the DC. output terminals 76 and 84 thereby energizing winding 94 and opening the normally closed contacts 92. Consequently, the above noted trouble circuit is interrupted deenergizing relay winding 48 (FIG. 3), closing contacts 47 and lighting trouble lamp 46. Similarly, in the absence of a DC. operating voltage in any suppressor unit control system 30 (FIG. 4), the relay winding 95 (FIG. 5) connected across detector terminals 81 and 82 is deenergized to open normally open contacts 91 and thereby interrupt the trouble circuit including the relay winding 48 (FIG. 3). Again, an indication of the trouble is given by the resultant closing of switch contacts 47 and lighting of signal lamp 46.

It will be appreciated that a similar trouble signal is provided upon a break in any of the lines comprising the above noted trouble circuit. In addition, a trouble signal is provided upon interruption of the lines in detector cable 40 that join the detector terminals 81 and 82 since such an interruption deenergizes relay winding 93 (FIG. 5) and opens normally open contacts 91 as described above.

The trouble circuit is interrupted also and the signal lamp 46 energized in response to opening of the normally open contacts 105 in the end-of-line station 15 (FIG. 6). This occurs upon deenergization of relay winding 104 which is in a series circuit including the secondary winding 103 of the transformer 102, the lines joining all C terminals of the system and the lines connecting all H terminals of the system. Since terminals C and H are themselves connected together in the ramp alarm station 14 (FIG. 3), the winding 104 is normally energized by current flowing in the secondary winding 103 and the normally open switch contacts 105 remain closed. However, upon loss of AC. voltage at the ramp alarm station 14 or upon interruption of any of the AC. supply lines connecting the AC. supply terminals C and D anywhere in the system, the transformer -2 in the end-of-line unit (FIG. 6) is deenergized. Consequently, secondary current flow through winding 104 is interrupted and contacts 105 open to cause lighting of signal lamp 46 as described above.

Thus, the signal lamp 46 is energized to provide an indication at the ramp alarm station 14 in response to any of variety of trouble conditions. These conditions include loss of AC. power, loss of DC. power anywhere in the system, interruption of any of the lines connecting the individual suppressor units 12 or interruption of any of the lines connecting detector terminals 64, 65, 81 or 82 of the individual control systems 30 and detector units 32.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, although portability is a primary feature of the invention, the protection system 11 disclosed could be installed as a permanent installation if desired. Also, condition responsive detectors other than those specifically mentioned can be used to activate the suppressor units 12. For example, a crash or g switch could be used to activate a suppressor system installed in aircraft. In such an arrangement, the system would automatically function in response to ground impact and thereby prevent the loss of life prompted by fire after many aircraft crashes. It is to be understood, therefore, that within the scope of the appended claims the invention can be practiced otherwise than as specifically described.

What is claimed is:

1. A fire protection system comprising a plurality of suppressor units each retaining a supply of a fire extinguishing medium, said suppressor units being dis tributed throughout the protected zone and including a plurality of electrically actuated actuators for automatically inducing discharge of said fire extinguishing medium from each of said suppressor units, condition responsive means for detecting an abnormal condition in the protected zone, and control circuit means connected between said condition responsive means and said actuators for actuating each of said actuators in response to detection of an abnormal condition by said condition responsive means.

2. A fire protection system according to claim 1 wherein said condition responsive means comprises a fire detection means.

3. A fire protection system according to claim 2 wherein said detection means comprises a separate detector unit associated with each of said suppressor units.

4. A fire protection system according to claim 3 wherein said actuators are electrically operated and said control system means comprises control circuit means connected between said fire detection means and said actuators.

5. A fire protection system according to claim 1 wherein said control circuit means comprises self-contained electrical power source means.

6. A fire protection system according to claim 5 wherein said power source means comprises a separate power source for providing operating power to each of said suppressor units.

7. A fire protection system according to claim 6 wherein said separate power sources are circuit isolated so as to prevent electrical current flow therebetween.

8. A fire protection system according to claim 7 wherein said control circuit comprises electrical connector means for connecting an external electrical power source to said separate power sources.

9. A fire protection system according to claim 8 wherein said control circuit means includes trouble circuit means for producing an electrical trouble signal in response to abnormalities in said control circuit means.

10. A fire protection system according to claim 9 wherein said trouble circuit means comprises electrical switch means for producing said trouble signal in response to the absence of operating electrical power at any of said suppressor units.

11. A fire protection system according to claim 1 wherein said fire extinguishing medium is a liquified gas and said suppressor units contain said liquified gas in quantities such that upon complete discharge thereof said protected zone Will contain a substantially uni-form concentration of the extinguishing vapor in an amount of between 2 and 5% by volume.

References Cited UNITED STATES PATENTS 739,016 9/1903 MacWilliam 1697 1,431,180 10/1922 Pearson 1697 10 ORear -16916X MacCracken 1691 Scofield et a1. 16942X Globerman et a1. 16919 LLOYD L. KING, Primary Examiner US. Cl. X.R.

Disclaimer 3,605,901.Ge0rge J. Grabowski, Needham, William B. Osborne, Marlboro and Rex/bra Wilson, Framingham Centre, Mass. FIRE PROTECTION AP- PARATUS. Patent dated Sept. 20, 1971. Disclaimer filed Feb. 28, 1986, by the assignee, Kidde, Inc.

Hereby enters this disclaimer to claim 11 of said patent. [Oflicial Gazette May 13, 1986.] 

